Rotating sewing machine hook



Feb. I, 1966 F. GEGAUF, JR

ROTATING SEWING MACHINE HOOK Filed Deo. 20, 1962 2 r fl A ,ww/

Ma fm United States Patent Oiitice Patented Feb. l, i966 3,232,258RUE'ATENG SEWENG MACHHNE HGK Fritz Gegauf, fr., Steckleorn, Thurgau,Switzerland, asf

signor to Fritz Gegauf Ahtieugesellschaft Bernina- Nahniaschinenfabrik,Steckhorn, Thurgau, Switzerland lFiled Dec. 20, 19.62, Ser. No. 246,043Claims priority, application Switzerland, ian. 10, 1962, 249/62 4Claims. (Cl. 112--228) The prime object ofthe present invent-ion is torealize a rotating sewing machine hook that cannot jam the thread andconsequently block the sewing machine.

There are sewing machine hooks known in the art that have on4 threesides guiding paths rotating about the counter path of the bobbin casesupport which is stationary during the sewing operation. The playbetween the guiding surfaces of the hook and of the bobbin support issmaller in axial direction than it is in radial direction in order toascertain for a safe taking-over of the loop at the needle. In bothdirections this play always is smaller than the thickness of the threadsto be sewn. Such guiding paths have the great disadvantage that upon awrong thread supply which does not correspond to the actual need theupper thread is drawn into the hook path. Such faulty thread supplyappears particularly at the beginning of the sewing due to an incorrectattendance. As a result of such wrong thread supply, the upper threaddrawn into the path of the hook is jammed in the guiding path of thebobbin support and blocks the whole machine.

This blocking is the stronger the thicker the upper thread is. In mostof such cases of jamming, it is necessary to disassemble the hook inorder to remove thread rests. This operation is very complicated and maybe eifected only by an operator to whom such operation has been taught.In order to prevent such blocking, it has already been proposed toprovide the guiding path of the bobbin support with thread cuttinggrooves. Such cutting grooves were intended to sever the jammed threadso as to enable upon further sewing the thread rests to be removed fromthe guiding path. However, this step has not been successful inpractice. Also reduction of the supporting portion of the runningsurfaces was unsuccessful since even reduced guiding surfaces proved tobe able to jam the thread and to block the machine. In order to removethese latter drawbacks it has also been proposed to make the axialguiding paths fof the hook resilient. Such hooks are constructed in suchmanner that the guiding cover enclosing the hook shells is maderesilient and easy to disassemble. Radially extending longitudinal slotsare provided on the cylinder shell at the points where the guiding coveris secured. These slots are intended to make possible for this cylindershell to give way in axial direction. Now the resiliency of acylindrical body provided with several radial slots is very small andfurther this system may not be applied in many hooks so that even withsuch hooks blocking of the machine may not be safely prevented. As wellfor the manufacturer as also for the retailer and buyer `of sewingmachines with hooks of the above type, time losses and costs areinvolved for teaching the operator the correct attendance of themachine.

In the sewing machine according to the present invention such blockingis effectively prevented owing to the fact that an axial guiding surfaceof the guiding may give way to such an extent that the hook may entrainany thread that has penetrated into the path through the whole guiding.Thus the costly teaching of the retailer and buyer may be dispensedwith, which obviously is a substantial technical progress.

This progress is realized according to the invention in a rotatingsewing machine hook having a support for the lower thread bobbin and aguiding path therefor, by forming at least one axial guiding of the hookas a radially resilient split tension ring adapted to move axially toprevent blocking of the hook at the thread insert.

Other features and advantages of the invention will become apparent fromthe description now to follow of a preferred embodiment thereof, givenby way of example only, and in which reference will be made to theaccompanying drawing, in which:

FIGURE 1 is a front View of a rotating, sewing machine hook.

FIGURE 2 is a longitudinal section throughv the hook taken along theline lI-II in FIGURE l;

FIGURE 3 is a partial section through the tension ring of the hook, and

FIGURE 4 is a perspective view of a disassembled hook.

The drawings illustrate the invention as incorporated in a rotatingsewing machine hook such as used in known sewing machines designed formaking straight, zig-zag, or ornamental stitches. For example, theparticular conventional sewing machine parts illustrated are parts ofthe universally known BERNINA sewing machine, but are likewiserepresentative, essentially, of corresponding constructions used inother conventional sewing machines.

ln the drawing, reference numeral 1 designates the hook shaft projectingfrom the base plate of the sewing machine (not shown). On this shaft issecured the hook 2 with its hub 3 by means of a screw 4. The hook tip 5takes the upper thread from the needle (not shown). On the side of thehub 3 there is secured a hook disk 6 by means of a screw 7. The hook 2is formed with an axially extending annular surface 8 and a radiallyextending annular surface 9 as well as a proled tension ring 11 theplane surface l@ of which forms a second radially extending annularsurface. This guiding 8, 9, 10 receives a bobbin case support 12 havinga threesided guiding crown 13 and a holding member 14. The split tensionring 11 is lodged in the conical groove formed between a bevelled orconical bearing surface 15 and a horizontal surface 16. At the end ofthe tension ring 1l. there is arranged a cranked tap i7 engaging agroove 1S in the hook 2 in order to stop the hook, i.e. to prevent thering l1 from rotating relative to the hook 2. To the hook 2, there isfurther secured by means of two screws Ztl a member i9 destined todeflect the loop. The deector 21 of the member projects beyond the hooktip in order to ascertain a safe loop formation. The stem or tap 22 ofthe bobbin case support 12 carries the bobbin case 23 having a lockingmeans 24. The hollow space of the bobbin case 23 receives the lowerthread bobbin 25.

When the machine is used to sew, the described hook 2 operates in amanner known per se by running about the bobbin case support l2 lockedat the holding member 14 and cooperating with the stitch formationelements of the sewing machine (not shown) and more particularly withthe needle. The hook tip 5 takes the upper thread from the needle inform lof a loop, widens this loop and guides the thread about the bobbincase 23 whereby the tensioned lower thread is passed through the loop asis well known. The hook disk or washer 6 serves as a support for theupper thread loop. The loop deiiecting member i9 prevents the lowerthread from being seized by the hook tip 5. Finally the upper thread islifted by the take-up lever (not represented) so as to terminate thestitch. This cycle is repeated at each stitch.

If now the upper thread for example due to a wrong operation of themachine at the beginning of the sewing is drawn into the guiding paths8, 9, 10 of the hook 2 the actual guiding surface 10 -of the tensionring 1l may give way in accordance with the pressure produced anddepending on the strength of the thread. The tension ring 11 climbsalong the annular bevel surface 15 thereby reducing its diameter andaffording for suicient play to permit the jammed thread to be entrainedby the hook 2 and to be evacuated at the open point. Thereby the jammingof the upper thread between the guiding paths 8, 9, 10 of the hook 2 andthe guiding 13 of the bobbin case support 12 leading in machines havingrigid guidings to a blocking thereof, is effectively prevented. Thetension ring 11 gives way in response to the strength of the usedthread. As soon as the thread rests have been removed the proled tensionring 11 comes again to rest with its plane surface 10 on the horizontalsurface 16 of the hook 2 since the ring 11 is always and automaticallypressed into this base position by the bevelled surface 15.

I claim:

1. In a freely rotating sewing machine hook, a hook body; a lower threadbobbin-case carrier having an annular peripheral bearing rib; an annulartrack for said bearing rib formed by an internal annular shoulder insaid hook body and a guard ring in said hook body cooperable with saidshoulder and axially spaced therefrom; said ring forming the axiallyouter part of said track and being adapted to yield resiliently foraxially outward displacement relative to the hook body; said guard ringcomprising a split ring mounted axially inwardly of and engaging aconical inner bearing surface in said hook body, said conical bearingsurface converging in a direction axially outwardly of said hook body.

2. In a freely rotating sewing machine hook as claimed in claim 1, saidsplit ring having a cross sectional shape such as to provide a lineContact with said conical inner bearing surface of said hook body.

3. In a freely rotating sewing machine hook as claimed in claim 1, saidhook body being formed with a radially extending plane bearing surfaceintersecting said conical inner bearing surface, and said ring having aplane surface engaging said radial plane surface whereby to determinethe Width of said track.

4. In a freely rotating sewing machine hook, as claimed in claim 1, saidhook body being formed with a radial recess; a free end of said splitring being bent for engagement into said radial recess for restrainingrelative rotation of said hook body and said split ring.

References Cited by the Examiner UNITED STATES PATENTS 2,065,349 12/1936Southam et al 112-228 2,452,167 10/1948 Wainwright 112-228 2,743,6895/1956 Ruemmler 112-228 2,773,464 12/1956 Rabezzana 112-228 2,857,86912/1958 Odermann 112-228 3,097,619 7/1963 Cerliani 112-228 JORDANFRANKLIN, Primary Examiner. DAVID I. WILLIAMOWSKY, Examiner.

1. IN A FREELY ROTATING SEWING MACHINE HOOK, A HOOK BODY; A LOWER THREADBOBBIN-CASE CARRIER HAVING AN ANNULAR PERIPHERAL BEARING RIB; AN ANNULARTRACK FOR SAID BEARING RIB FORMED BY AN INTERNAL ANNULAR SHOULDER INSAID HOOK BODY AND A GUARD RING IN SAID HOOK BODY COOPERABLE WITH SAIDSHOULDER AND AXIALLY SPACED THEREFROM; SAID RING FORMING THE AXIALLYOUTER PARTLY OF SAID TRACK AND BEING ADAPTED TO YIELD RESILIENTLY FORAXIALLY OUTWARD DISPLACEMENT RELATIVE TO THE HOOK BODY; SAID GUARD RINGCOMPRISING A SPLIT RING MOUNTED AXIALLY INWARDLY OF AND ENGAGING ACONICAL INNER BEARING SURFACE IN SAID HOOK BODY, SAID CONICAL BEARINGSURFACE CONVERGING IN A DIRECTION AXIALLY OUTWARDLY OF SAID HOOK BODY.